The prevalence of metabolic diseases has reached epidemic proportions in the United States. In cells, nutrients are stored as triacylglycerol (i.e. at) in lipid droplets (LDs), a conserved endoplasmic reticulum-derived organelle that is consists of a neutral lipid core encircled by a phospholipid monolayer decorated with regulatory proteins. Storage of triacylglycerol in LDs is not only critical for energy production and as a source of membrane precursors, but is central to the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disease, and has been linked to aging and cancer. For years LDs were thought of as inert cytoplasmic fat globules and there was little interest among the scientific research community. The recognition that LDs are integrally involved in the etiology of multiple diseases and that LDs are extremely dynamic organelles has paved the way for a burgeoning area of research with the potential to make a significant impact on future treatment strategies for metabolic diseases. LDs fundamentally function as hubs of cellular lipid metabolism, and it is essential that we understand the mechanisms that regulate LD biogenesis and function. Therefore, my proposed research will specifically: 1) Exploit advanced functional genomic strategies to generate a high-density epistatic map of all genes required for LD biogenesis in human cells, 2) Use metabolomics technologies to define the functional impact of ER-LD ubiquitination machinery in LD biogenesis and lipid metabolism, and 3) Utilize proximity labeling proteomic methods to define ER subdomains specialized for LD biogenesis and to determine the temporal dynamics of LD proteome maturation. Integration of these complementary studies will break new ground in cell biology and metabolic disease treatment strategies by advancing our understanding of the mechanisms underlying LD biogenesis and the molecular basis of LD dysfunction in human diseases.